1. Field of the Invention
This invention relates to a vibration switch, more particularly to a vibration switch with two electrically conductive rollable bodies which abut against two tangential areas of two electric contact bodies to establish electric contact between the electric contact bodies, and which will lurch towards a farthermost area of a respective one of the electric contact bodies when the vibration switch is in an unsteady state so as to break the electric contact.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional vibration switch 1 is shown to include a metal housing 11 with an accommodation chamber 111 for receiving a deflectable electric contact body 12, such as a coil spring. An anchoring end 121 of the electric contact body 12 is sleeved on a plug portion 112 of the housing 11 such that a contact terminal end 122 thereof is held along an axis. A first electric contact terminal 113 extends from a side wall of the housing 11 downwardly. A second electric terminal 14 has a contact end inserted into the contact terminal end 122 through a through hole 131 in an insulating plug member 13.
As shown in FIG. 3, when the housing 11 is jerked by a force (F), the contact terminal end 122 of the electric contact body 12 is deflected radially as a result of an inertial force so as to contact the second electric terminal 14, thereby establishing an electrical connection between the first and second electric contact terminals 113,14. However, when the housing 11 is jerked by a force (not shown) from a direction substantially parallel to the axis, the extent of deflection of the contact terminal end 122 is relatively small so that the contact terminal end 122 may not be able to contact the second electric terminal 14 to establish the electrical connection between the terminals 113,14.
The object of the present invention is to provide a vibration switch which can be instantly disposed in a switch-off state when jerked by a force coming from any direction.
According to this invention, the vibration switch is adapted to be disposed in electric contact with a support, and includes a housing adapted to be mounted on the support in an upright direction. The housing includes an upper wall and a lower wall spaced apart from each other in the upright direction to confine an accommodation chamber.
First and second electric contact bodies are disposed in the accommodation chamber, and respectively have first and second rolling surfaces that are spaced apart from each other along a centerline which is oriented in one of the upright direction and a longitudinal direction that is transverse to the upright direction. The first and second rolling surfaces respectively define first and second farthermost areas which are spaced apart from each other by a first length along the centerline, and respectively define first and second tangential areas which are offset from the centerline. The first and second tangential areas are spaced apart from each other by a distance that, when projected on a longitudinal line in the longitudinal direction, is equivalent to a second length.
First and second electrically conductive rollable bodies are respectively rollable on the first and second rolling surfaces about first and second rolling axes, and respectively have first and second perimetrical areas which are in contact with the first and second rolling surfaces, and first and second widths. Each of the first and second widths is defined by a distance which is between two diametrically opposite points in a respective one of the first and second perimetrical areas. Sum of the first width and the second width is smaller than the first length and larger than the sum of the second length and the third length. As such, when the support on which the housing is mounted stands still, the first and second electrically conductive rollable bodies are tangent to each other, and respectively abut against the first and second tangential areas by virtue of gravity, thereby establishing electric contact between the first and second electric contact bodies. Once the support is caused to quiver in an unsteady state, the first and second electrically conductive rollable bodies will be caused to lurch towards one of the first and second farthermost areas so that one of the first and second electrically conductive rollable bodies is out of contact with a corresponding one of the first and second rolling surfaces which defines the other one of said first and second farthermost areas, thereby breaking the electric contact between the first and second electric contact bodies.